There are two prominent people in the Bible named Saul. One was the first king of the land of Israel. The other was the first-century evangelist, whose name later was changed to Paul.
Saul - the king - was the first king of Israel. He was the son of Kish of the tribe of Benjamin. He became king at about the time that Samuel had retired as the last Judge of Israel. Although the land of Israel had been ruled by judges, the people were clamoring to have a king, like other nations. Samuel asked the Lord for advice. God directed Samuel to Saul and to anoint him as the first king.
Saul, his army, and a miracle from God, defeated the Philistines in their first battle. He then defeated Moab, Ammon, Edom, the kings of Zobah, and the Amalekites. However Saul did not obey the Lord, and kept some of the loot after defeating the Amalekites. For this, God rejected Saul as king of Israel. The Lord had Samuel anoint young David as the next king.
After David killed Goliath, Saul made David his special assistant, and as David succeeded in everything he did, Saul grew extremely jealous. Saul became possessed by an evil spirit, went into fits of anger and tried to kill David several times. He even threw a spear at his own son Jonathan, who had become David's close friend.
After Samuel died, the Philistines invaded Israelite territory and gathered forces at Shunem. Saul had a foreboding of his fate, and as he did not have Samuel to ask God for advice, he traveled to En Dor to consult a witch about the outcome of the battle. The result of the seance confirmed his worst fears, he was told that the entire Israel army would be routed by the Philistines, and that he and his three sons would be killed.
The Israelite army had no chariots and could not withstand the assault of the heavy Philistine weaponry. On Mount Gilboa, Saul and his three sons were killed. Their bodies were brought to Jabesh where they were cremated. David after learning of Saul's death, moved to Hebron and was crowned king of the Judean confederacy.
The story of Saul is found in 1 Samuel, chapters 9-31.
In the New Testament, there is a man named Paul, also known as Saul, who was born in Tarsus of Cilcia in Asia Minor. His family was of the line of Benjamin. He grew up in Jerusalem and studied Jewish tradition under the elder Gamaliel, becoming a zealous Pharisee. Paul was at first an active opponent of the Christian movement. He took care of the cloaks of those who threw stones at Stephen (Acts 7:58, 22:20).
On his way to Damascus to persecute Christian believers, he was stopped by a blinding light, and a voice that said, "Saul, Saul, why do you persecute Me?" Paul asked, "who are You Lord?" The reply came, "I am Jesus, whom you are persecuting. But get up and enter the city, and you will be told what you are to do." Paul then converted to Christianity. And his zeal to persecute the early Christians was re-channeled into preaching the Gospel.
Paul made three missionary journeys around Asia Minor, Macedonia and Achaia. He is the author of thirteen New Testament letters - Romans, 1 and 2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1 and 2 Thessalonians, 1 and 2 Timothy, Titus, and Philemon. It is also possible he might have wrote Hebrews. With the exception of Romans, all of Paul's letters were written to churches or individuals whom he knew personally.
The focus of Paul's writings is Jesus, through whom God has effected redemption for all people regardless of ethnic or social background.
Paul was thrown into prison, whipped, stoned, punched, and shipwrecked many times, but never gave up his preaching of Christ. He might have been the most zealous and hardest working Apostle of all time. It is believed that Paul was beheaded in Rome under Nero in about AD 67.